Photographic gelatin hardened with an aliphatic polyoxymethylene glycol aliphatic carboxylic acid diester



United States Patent i thee 3,539,351 Patented Nov. 10, 1970 ABSTRACT OFTHE DISCLOSURE Gelatin compositions and photographic silver halidegelatin emulsions are hardened upon the alkaline activation of certainpolyoxymethylene esters.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to organic materials which are particularly useful in thephotographic field and to gelatin compositions containing therein acompound useful for hardening gelatin under alkaline conditions, buthaving little or substantially no hardening action under neutral oracidic conditions.

Description of the prior art It is desirable that a layer of gelatin ina photographic element remain on the support during processing atelevated temperatures, and this is usually done by hardening the gelatinbefore or during processing. Known hardening substances have beenincorporated in gelatin compositions, but many of these have producedundesirable sensitometric effects when contacted with photographicemulsions, as well as producing substantially immediate hardening thusincreasing processing times. Formaldehyde, for instance, has shownadverse sensitornetric characteristics in contact with certain highlysensitized photographic emulsions. Other hardeners have exhibitedtendencies to fog and otherwise create objectionable sensitornetriceffects. Still other hardeners produce an immediate hardening effectupon their incorporation into the photographic emulsion, or upon agingor storage.

Gates and Rees, U.S. Pat. 3,110,597, issued Nov. 12, 1963, discloses aspotential gelatin hardeners, compounds containing the acyloxy moiety,which compounds affect the gelatin emulsion upon contact with liquidsexhibiting an alkaline effect. This reference, however, shows onlymono-oxymethylene esters which require a halogenated acid moiety. Wehave found that in our novel compositions containing our blockedhardening agents, polyoxymethylene diesters provide results superior tothose afforded by the monooxymethylene esters.

SUMMARY OF THE INVENTION According to our invention we have now foundthat compositions comprising a hardenable material such as aproteinaceous material, for example, gelatin and more particularlygelatin silver halide emulsions, are satisfactorily hardened byactivating certain blocked-hardeners during processing. These hardenersare aliphatic polyoxymethylene diesters which are particularly effectiveunder alkaline conditions to harden protein and, in photographicbinders, are capable of delivering rapid image formation.

DESCRIPTION OF PREFERRED EMBODIMENTS Our invention is accomplished byadding an aliphatic polyoxymethylene glycol aliphatic carboxylic aciddiester to a hardenable material, for example, proteinaceous materialssuch as gelatin, gelatin derivatives and the like. The term gelatin asused in our invention includes not only gelatin, per se, but gelatinmixtures and derivatives as hereinafter described.

The aliphatic polyoxymethylene glycol-carboxylic acid diesters of ourinvention include those having the following formula:

in which R is lower alkyl (e.g. alkyl of 1 to 3 carbon atoms), orhaloalkyl and n is in integer of from 2 to 20. Typical alkyl groupsinclude methyl, ethyl, n-propyl, isopropyl, and haloalkyl groups such aschloromethyl, chlo roethyl, trichloromethyl, etc. Compounds of the abovegeneral formula can be prepared as previously described in theliterature.

In accordance with this invention it has been found that our diesterscan be used to treat hardenable materials such as hydrophilic colloidsas exemplified by gelatin. In alkaline media the binding agents inphotographic materials are hardened by the compounds of this invention.The hardening, or crosslinking, effect occurs between the hardenablematerial and an aliphatic polyoxymethylene glycol aliphatic carboxylicacid diester of the invention. In another aspect of this invention, wehave found a method of hardening a hardenable material which comprisestreating said material with a compound having the formula disclosedabove. This hardenable material can comprise a layer on a support in aphotographic element, for example, the layer can comprise a photographicsilver halide emulsion.

The hardening effect is thus substantially delayed or blocked andappears concurrently with processing and during the image developmentstage. This results in a re duced time required for processing, adiminution of deleterious sensitornetric elfects and less destruction ofthe generated hardening substance in the alkaline processing medium.Where gelatin is used in the composition as the binding agent forphotographic emulsions, a useful range of blocked hardener is from 0.5to 10 percent, based on the weight of the gelatin. Activation of theblocked hardener occurs preferably at a pH of about 10, a useful rangebeing about 7 to 14.

As will be understood by those skilled in the art, no essential factorsexist for obtaining a suitable pH. For example, the pH can be adjustedprior to, during or after the addition of the hardening compounds to thehardenable material.

The following examples are illustrative of the invention, but othersimilar compounds may be used both singly, and in combination ashereinafter shown.

Although frequently obtained in mixtures, the compounds of the inventioncan be fractionally distilled in many cases into substantially pureesters and used as such.

Example I.A preparation of dioxymethylene diacetate is effectedfollowing the procedure described by Tomiska and Spousta, Angew. Chem.74, 248 (1962) for reacting s-trioxane with acetic anhydride. Thedioxymethylene diacetate was recovered having a boiling point ofapproximately 54-56 C. (0.7 mm.).

Example II.In the same procedure as shown in Example I, there is alsorecovered trioxymethylene diacetate, possessing a boiling point ofapproximately 62-63" C. (0.07 mm).

Example lII.According to an adaptation of Standinger et al., Ann. 474,(1929) a mixture of paraformaldehyde and acetic anhydride is heated atC. for approximately 1 /2 hours. The soluble portion of this product isextracted with ether, the latter then evaporated,

and the residue taken up in ethyl acetate. Upon distillation of thissolution, several fractions are recovered, each of which consist chieflyof a twoor three-component mixture of polyoxymethylene diacetates.

(A) Distillation at a pot temperature of 99 C. (4n) (all of theremaining values for vacuum area in microns ,to) produce a compositionconsisting of approximately 14 percent tri-, 63 percent tetraand 23percent pentaoxymethylene diacetates which is indicated by vapor phasechromatography.

(B) Continued distillation of the above solution in Example HI producesanother fraction at 115 C. (4 which is found to consist of approximately55 percent pentaand 44 percent hexaoxymethylene diacetate.

(C) Distillate fractions detected at about 152 C. (7 consist of about 45percent hexaand 53 percent heptaoxymethylene acetates.

(D) The last distillate fraction from the reaction of Example III(above) is recovered at a pot temperature of 168 C. (4n) and is a lowmelting, semi-crystalline solid. Chromatographic identification meansresult in identifying approximately 31 percent heptaand 69 percentoctaoxymethylene diactetates.

Example IV.Mono-oxymethylene diacetate is obtained by fractionation ofthe forerun obtained in Example III; B.P. 65 mm.).

Example V.Dodeca(oxymethylene)diacetate is ob- 4 semi-solid extractedwith ether. Fractionation of the ether extracts produce severalfractions, one of which proves to be his (chloroacetoxy)rnethane with aboiling point of 66-68 C. (1 n 1.4662.

The structure is confirmed by elementary analysis and by the nuclearmagnetic resonance spectrum.

Example VIII.A higher boiling fraction from the ether extracts ofExample VII which solidifies, is recrystallized from ether. Thisfractions structure is shown by elementary analysis and by nuclearmagnetic resonance to be that ofocta(oxyrnethylene)-bis-(chloroacetate).

It was found that similar compounds, containing the mono-oxymethylenegroup (where n is one) rather than the polyortymethylene ester, uponincorporation into a gelatin composition, and more particularly, asilver halide photographic gelatin emulsion, provided substantially nohardening either immediately or upon immersion in an alkaline medium.

The compounds prepared in the preceding examples were added to separateportions of a high-speed silver bromoiodide emulsion panchromaticallysensitized with a cyanine dye. Each emulsion sample was coated on acellulose acetate film support at a coverage of 432 mg. of silver and980 mg. of gelatin per square foot. A sample of each film coating wasexposed on an Eastman IB sensitomere, processed for five minutes inKodak D-l9 developer, and dried with the following results:

Sensitometric data, fresh Percent swell Rel. Wash Compound used Percent1 speed Gamma Fog Dev. Fix water Control 100 1. 18 13 600 390 650Dioxymet-hylene diaeetate 6 102 1. 12 380 260 410 Trioxymethylenediacetate 6 112 1. 23 11 350 240 360 Mono-oxymethylene diaeetate 6112 1. 11 540 350 590 Control. 100 1. 57 16 460 320 510 Mixed trl-tet-raand pentaoxymethyleno d1- acetates 6 89 1. 43 13 360 260 410 Mixedpentaand hexaoxy-methylene diacetates 6 89 l. 37 13 380 250 400 Mixedhexaand heptaoxy-methylene diaeetates 6 94 1. 48 13 350 250 390 Mixedheptaand octaoxy-methylene diaeetates 6 100 1. 57 14 380 260 420 1 Basedon weight of dried gelatin.

Similarly, other examples previously cited give the same good hardeningresults in the absence of deleterious sensitornetric effects.

In a similar series of experiments, in which the developer used wasKodak DK-SO, the following results were obtained:

Sensitometric data, fresh Percent swell Wash Compound used Percent 1Speed Gamma Fog Dev Fix water Control 100 1. 22 l4 1, 400 580 910 1147 1. 3O 14 1, 100 490 790 Dioxymethylene diacetate. 3 297 1. 27 14 960440 670 6 95 l. 23 l4 1, 510 710 Trioxy-methylene diacetate 3 94 1. 2313 830 360 570 6 97 1. 23 14 900 420 620 Monooxymethylene diacetate 3 1.32 14 1, 300 540 880 6 102 1. 32 14 1, 200 490 800 1 Based on weight ofdried gelatin.

Example Vl.From the ether extraction of Example V, a residue isextracted with chloroform at 25 C. Upon evaporation andrecrystallization from the chloroform, a colorless solid extract isproduced having a melting point of 98100 C. This solid isheptadeca(oxymethylene)diacetate (Staudinger et a1. reports 98.599.5 C.for this compound.)

Example VII.Bis(chloroacetoxy)methane is produced as folows: A mixtureof 300 parts of chloroacetic anhydride and 265 parts of paraformaldehydeis heated at C. for 1 hour in a stirred autoclave. The reaction Thesilver halides employed in the photographic emul- 65 sions include anyof the photographic silver halides, as

exemplified by silver bromide, silver chloride, silver chlorobromide,silver bromoiodide and the like. The silver halides used can be thosewhich form latent images predominantly on the surface of the silverhalide grains or those which form latent images inside the silver halidecrystals such as described in U.S. =Pat. 2,592,250 of Davey and Knottissued Apr. 8, 1952.

Photographic emulsions of the present invention can contain antifoggingand stabilizing agents and can be product is washed with petroleum etherand the residual 75 sensitized using any of the well-known techniques inemulsion making, for example, by digesting with naturally active gelatinor various sulfur compounds and/or gold compounds. The emulsions may besensitized with salts of novel metals of Group VIII of the PeriodicTable which have an atomic weight greater than 100. The emulsions canalso be sensitized with labile selenium and noble metals as disclosed inUS. Pat. 3,297,446 of Dunn issued Jan. 10, 1967. The emulsions may alsocontain speed-increasing addenda such as quaternary ammonium salts,polyethylene glycols, or thioether sensitizers.

The emulsions of the invention may also contain conventional additivessuch as gelatin plasticizers, additional hardeners and coating aids.These emulsions may be used in X-ray and other non-optically sensitizedemulsions, and may also be used in ortho-chromatic, panchromatic andinfrared sensitive emulsions. The additives may be added to the emulsionbefore or after sensitizing dyes, if any, are used.

The emulsions may be used in photographic elements intended for colorphotography, and thus may contain color-forming couplers, or used asemulsions to be developed by solutions containing couplers or othercolorgenerating materials, or emulsions of the mixed-packet type, asdisclosed in US. Pat. 2,698,794 of Godowsky issued Jan. 4, 19 55, oremulsions of the mixed-grain type, such as disclosed in US. Pat.2,592,243 of Carroll and Hanson issued Apr. 8, 1952.

The emulsions obtained in accordance with this invention may be used indiffusion transfer processes which utilize the undeveloped silver halidein non-image areas of the negative to form a positive by dissolving theundeveloped silver halide and precipitating it on a silver layer inclose proximity to the original silver halide emulsion layer. Suchprocesses are described in US. Pats. 2,352,014 of Rott issued June 20,1944; 2,543,181 of Land issued Feb. 27, 1951; and 3,020,155 of Yackel etal. issued Feb. 6, 1962. The emulsions may also be used in diffusiontransfer color processes which utilize a diffusion transfer of animagewise distribution of developer, coupler or dye, from alight-sensitive layer to a second layer, while the two layers are inclose proximity to one another.

A wide variety of emulsion vehicles and dispersing agents for silverhalide grains may be employed singly or in combination with each other,for example, gelatin, colloidal albumin, cellulose derivatives andsynthetic resins, such as polyvinyl compounds. The blocked hardeners ofthis invention are effective with polymeric substances used incombination with gelatin in photographic emulsions, or otherwise asnoted in Smith application U.S. Ser. No. 525,272, filed Dec. 20, 1965US. Pat. 3,459,790. Also, our blocked hardeners can be used with gelatinderivatives, such as those described in Yutzy and Frame US. Pat.2,614,928, issued Oct. 21, 1952. Examples of typical colloids which maybe used are poly(vinyl alcohol), hydrolyzed poly(vinyl acetate),hydrolyzed cellulose ester, water-soluble ethanolamine celluloseacetate, polyacrylamide, copolymers having a combined acrylamide contentof 3-60 percent, copolymers of alkyl acrylate and acrylic acid, a vinylalcohol copolymer containing urethane carboxylic acid groups orcontaining cyanoacetyl groups, or polymeric material which results frompolymerizing a protein or saturated acrylated protein with a monomerhaving a vinyl group such as disclosed in US. Pat. 2,852,382 of Jonesissued Sept. 16, 1958. Such polymeric additives may be employed aslatices or hydrosols in the preparation of the photographic emulsions ofour invention.

The photographic emulsions can be coated on a wide variety of supports,preferably supports which are transparent and/or flexible. Typicalsupports include metals such as aluminum, paper, cellulose acetate film,polyvinyl acetate film, polystyrene film, polypropylene film and otherpolyolefin film, polycarbonate film, polyethylene terephthalate or otherpolyester film and other related materials. Supports such as paper whichare partially acetylated or coated with an alpha-olefin polymerparticularly a polymer of an alpha-olefin containing 2-10 carbon atoms,as exemplified by polyethylene, polypropylene, ethylenebutene copolymersand the like, give good results.

Further these agents can be used in the preparation of various subbinglayers for silver halide emulsions, interlayers, filter layers or inovercoat layers.

Although the invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof,variations and modifications can be effected within the spirit and scopeof the invention as described hereinbefore and as defined in theappended claims.

We claim:

1. A gelatin containing composition comprising a hardening concentrationof an aliphatic polyoxy-methylene glycol aliphatic carboxylic aciddiester.

2. A gelatin composition containing in hardening concentration therein apolyoxymethylene diester having the structure:

in which R is lower alkyl being unsubstituted or containing a halogensubstituent, and n is an integer of from 2 to 20.

3. A gelatin silver halide photographic emulsion comprising therein ahardening concentration of a polyoxymethylene diester having thestructure:

in which R is lower alkyl being unsubstituted or containing a halogensubstituent, and n is an integer of from 2 to 20.

4. The emulsion described in claim 3 wherein R is methyl and n is 2.

5. The emulsion described in claim 3 wherein R is methyl and n is 3.

6. The emulsion described in claim 3 wherein R is methyl and n is 4.

7. The emulsion described in claim 3 wherein R is methyl and n is 5.

8. The emulsion described in claim 3 wherein R is methyl and n is 6.

9. The emulsion described in claim 3 wherein R is Ris in which R islower alkyl being unsubstituted or containing a halogen substituent, andn is an integer of from 2 to 20.

(References on following page) 7 8 References Cited NORMAN G. TORCHIN,Primary Examiner UNITED STATES PATENTS R. E. FICHTER, Assistant Examinerl. 29 3,110,597 11/1963 Gates at a 96 X Us. CL XlR 3,442,654 5/1969Eiseman et a1 96114X 3,471,297 10/1969 Sprung 96-107 5 106-125; 260117

